Bookbinding systems are already present in which a bookbinding device is connected to an image forming device in an online manner, and the sheets after image formation ejected from the image forming device are bound into the form of a booklet by stitching the bundle of sheets in a bookbinding device. One bookbinding method by the use of such a bookbinding system is a method by stitching heating and pressing against the edge parts of the bundle of sheets a tape (the binding tape) which has a base material of paper or cloth cut in the form of a tape coated with a hot melt type adhesive that becomes soft and melts by heating, and this method is usable for binding very important papers because, even when the number of pages is large, there is no limitation due to the length of the stapling wire and also the appearance or the finish of the bound book is good.
In the method of bookbinding using a binding tape, the sheets with images formed on them and ejected by an image forming device on the upstream side are successively stacked one upon another, and after a bundle of sheets is formed by arranging the sheets, they are bound by pressing a binding tape against the edge part of the bundle of sheets while heating and pressing the binding tape by a heating member thereby transferring to the bundle of sheets the hot melt type of adhesive that has become soft and has been melted by heating. The heating member is separated from the binding tape after the transfer of the adhesive to the bundle of sheets has been completed. Since the temperature of the hot melt type adhesive returns to room temperature when the heating member is separated from it, the adhesive is hardened whereupon the binding tape and the bundle of sheets get fixed to each other thereby completing the binding operation.
Most binding means are a type which binds the edge portion of a bundle of sheets by a stapler or a type which binds a bundle of sheets by coating a hotmelt adhesive on the front edge surface the bundle. Further, there is offered means which coats glue at the edge portion of sheets ejected from an image forming device, stacks the sheets while arranging them, and finally presses the edge portion, of the sheets, having the glue coated thereon to bind the bundle of sheets (for example, see Patent Document 1). The above described respective means have respective features, allowing it to select a proper means, depending on a purpose of bookbinding.
The heating member is heated and melts the adhesive of the binding tape by pressing it against the binding tape. The heating member is needed to heat the binding tape uniformly within a short time, and accordingly aluminum having a satisfactory thermal conductivity or stainless steel having a satisfactory thermal accumulation property is used as the material of the heating member. The member is heated by providing heaters on the surface opposite to this surface in contact with the binding tape.
Since the member is required to have the strength necessary for withstanding the pressure of pressing against the binding tape and also to have a uniform temperature distribution, its thermal capacity becomes large. As a consequence, the time from starting the current flow to the heater until the member reaches a predetermined temperature suitable for bookbinding, that is, a so-called warming-up time is long, and hence sometimes the waiting period becomes long before starting image forming operations even when preparation has been completed in the image forming device.
As a measure to shorten the warming-up time of post-processing devices as much as possible under limited conditions, there have been proposals in which a plurality of heaters are provided for the heating member of a post-processor and the temperature of the entire heating member is raised uniformly by controlling the distribution of power supplied to these heaters (for example, see Patent Document 2).
Patent Document 1: Japanese Unexamined Patent Application Laid-Open TOKKAI No. 2003-291558 (Page 1-2)
Patent Document 2: Japanese Unexamined Patent Application Laid-Open TOKKAIHEI No. 9-323488 (Page 1).
In order to shorten the warming-up time of the post-processor described in Patent Document 1 and Patent Document 2, although it is possible to consider increasing the capacity of the heaters and supplying a larger power, normally, there is a limit on the power supply capacity of the power distribution-panel or the power supply socket to which the device is connected, and hence the power that can be used for this will naturally be limited. In particular, when a post-processor is connected to an image forming device having a fixing unit that uses heated rollers, since it becomes necessary to supply electric power for warming-up to a plurality of heaters at the same time, the electric power that can be supplied to each individual heater is limited, and hence it is likely that the overall warming-up time of the entire image forming system including an image forming device and a post-processor is longer in spite of taking this measure.
In addition, depending on the environment of use by the user, there are cases where a post-processor that binds the bundle of sheets using a hot melt type of adhesive is always used and there are cases where such a device is not always used. In the case where a post-processor is always used, it is required that the warming-up of the post-processor is completed in a short period of time. In the other case where it is not always used, it is necessary that the power consumption be reduced to the lowest possible limit during when the post-processor is not used.
The present invention was made with consideration of the above conditions, and a first object of the present invention is to provide an image forming system in which it is possible to complete warming-up of the image forming device in a short time under conditions in which there are limitations on the usable electric power. In addition, a second object of the present invention is to provide an image forming system in which it is possible to save the electric power consumed in the heating section of a post-processor under conditions where the heating section of the post-processor is used at long intervals.
On the other hand, in a bookbinding system in which a bookbinding device is connected to an image forming device, the power supply of the bookbinding device is generally switched on when the power supply of the image forming device is switched on. If the bookbinding system is started due to either switching on the power of the image forming device or start from a low consumption power mode such as a power saving mode or a sleep mode, the warming-up of the image forming device and the warming-up of the bookbinding device are started simultaneously. In a known bookbinding system, the power consumption during warming-up is high because the supply of electric power to the image forming device and to the heating units of the bookbinding device are started at the same time as switching on the power of the image forming device or start from an energy saving mode. In particular, at the time the power supply is switched on or at the time of starting from a low consumption power mode, since the temperatures of the heater of the heating units of both devices are low, the power consumption becomes even higher and hence the power consumption in a bookbinding system becomes a maximum at the time the power supply is switched on or at the time of starting from a low consumption power mode.
However, when installing a bookbinding system, the user has to select an image forming device and a bookbinding device based on a usable power distribution panel or an electric power that can be supplied from a power socket. Even when the power supply capacity of a power distribution panel or a power supply socket is limited, an image forming device may be installed, depending on the power supply capacity of the power distribution panel or the power supply socket. However, if a bookbinding device is added, the power consumption may exceed the amount of electric power that can be supplied. In such a case, the user is forced either to give up the introduction of a bookbinding system or to enable the introduction by carrying out facility enhancement work of increasing the power supply capacity of the power distribution panel or of the power supply socket.
On the other hand, as a method of reducing the power supplied from a commercial power supply to an image forming device, it has been proposed to heat the fixing units of the image forming device using a main heater driven by power from the commercial power supply and an auxiliary heater driven by DC current supplied by a built in storage battery (see, for example, Patent Document 3), this would require a circuit unit for rectification and charging and a storage battery circuit unit, whereby the construction becomes unavoidably complicated. In addition, although it is possible to reduce the maximum power consumption by properly distributing the power supplies given to the image forming device and the bookbinding device constructing the bookbinding system while monitoring the temperatures of heaters of both devices, such a method is not practical, as it would require a complicated structure. So far there has been no bookbinding system that can reduce the maximum power consumption, with a simple structure.
In this manner, there is a desire to connect a bookbinding device having a heating unit to a known image forming device and use them as a bookbinding system. However, depending on the power supply capacity of a power distribution panel or of a power supply socket that can be used, there are many limitations imposed on users, requiring them either to give up their desire or to carry out facility enhancement work of increasing the power supply capacity of the power distribution board or of the power supply socket.
Patent Document 3: Japanese Unexamined Patent Application Laid-Open TOKKAI No. 2000-98799
In this point of view, a third object of the present invention is to reduce the maximum power consumption in an image forming system having an image forming device and a bookbinding device that includes a heating section while having a simple system structure.